Conveying devices, such as those which are used for moving objects between different stations in a factory, usually comprise a conveying track in the form of a belt or a chain. The conveying tracks can be recessed in a trench with vertical side surfaces. Alternatively, they can be located on the horizontal upper surfaces of the trench or arranged in some other way. The objects to be conveyed are arranged slidably in relation to the conveying tracks, either directly or via supporting means. Larger objects are often conveyed on supporting means also known as pallets, and smaller objects may be conveyed using a small carrier often referred to as a carrier puck.
A supporting means is conveyed along the conveying track, which may comprise different work stations. The work stations may be positioned along the conveying track such that all objects will pass all work stations. In this way, all objects must stop at the same time, regardless if an object is to be manipulated at a work station or not. Such an arrangement is not very flexible and is mostly used when all objects are to be manipulated in the same manner, and when the manipulation requires only a short time duration.
In more flexible systems, where different work stations can perform different operations on different objects, the work stations are separated from the main conveyor track. In such a system, each object can be directed to any work station without disturbing the flow on the main conveyor track. The duration of an operation at a work station will thus not affect the other objects. An object is directed into a side track by a diverting station. In order to be able to divert an object into a side track, the diverting station must be able to catch the right object from the main object flow and to move it out of the flow. If there are many objects travelling next to each other in the main flow, bearing on each other, the force required to move the puck out of the flow will be relatively high.
In some systems, a circular diverter disc having one or more grip openings is used to divert the pucks from the main conveyor track. In such systems, the pucks are circular such that they can be gripped by the diverter disc. The opening in the diverter disc is semi-circular and corresponds to the size and shape of the puck.
When a diverter disc grips the puck and moves it out of the main flow, the puck will be subjected to a rotational movement since the diverter disc rotates. The puck may rotate during the diversion but will most likely not rotate in relation to the diverter disc. With several other pucks bearing on the first puck, the diverter disc will have to overcome the force from the rest of the pucks that are pushed towards the first puck by the conveyor. This will lead to either that the first puck glides with a friction against the other pucks or that all the other pucks will be rotated by the first puck, or a combination of both. When a puck rotates, it will rub against the conveyor rails and possible against the neighbouring pucks. In either case, a relatively high force must be exerted by the diverter disc due to the friction between the pucks and the force applied on the pucks by the conveyor track in the direction towards the first puck.
One way of solving this problem is to introduce an extra stop function before the diverter station. The stop will interrupt the main flow such that a single puck can easily be directed out from the main conveyor track. Each stop is however an unnecessary cost and it also requires additional space.
Another possibility is to use a motor that is strong enough to overcome the force from the pucks in the main flow. When other pucks bear on the first puck, the diverter disc must overcome the force from all other pucks during the diversion. This requires a relatively large drive unit. In a large system having several work stations, the total power requirement will thus be unnecessarily high. When a first puck is diverted out of the main flow by a diverter disc, the diverter disc must apply a rotational torque that can overcome the force of the puck train acting on the first puck, either by rotating the pucks in the puck train, by sliding the first puck against the puck train or by sliding the first puck in the diverter disc.
DE 4329078 A1 describes such a diverter disc that is used to divert circular pucks by catching one puck at the time and to divert it in another direction. The remaining pucks will bear against the circumference of the disc.
U.S. Pat. No. 4,723,661 A also describes a similar diverter discs where a circular puck is diverted by the diverter disc and where the remaining pucks bear against the circumference of the disc.
U.S. Pat. No. 6,520,313 B1 describes a system in which such a diverter disc is used to divert circular pucks.
In all those documents, the puck is held by the semi-circular opening in the diverter disc. In order to obtain a low friction between the opening and the puck, the disc opening corresponds to the shape and size of the puck. This will minimize wear due to sliding between the disc opening surface and the outer puck surface.
These solutions work fine in some systems, but are anyhow subjected to the above mentioned problem. There is thus still room for improvements.